TAILIEUCHUNG - Lecture Human anatomy and physiology - Chapter 27: The reproductive system (part c)

Chapter 27 - The reproductive system (part c), the main contents of this chapter include all of the following: Establishing the ovarian cycle, establishing the ovarian cycle, hormonal interactions during a 28-day ovarian cycle, uterine (menstrual) cycle, effects of estrogens,. | 27 The Reproductive System: Part C Establishing the Ovarian Cycle During childhood, until puberty Ovaries secrete small amounts of estrogens Estrogen inhibits release of GnRH Establishing the Ovarian Cycle At puberty Leptin from adipose tissue decreases the estrogen inhibition GnRH, FSH, and LH are released In about four years, an adult cyclic pattern is achieved and menarche occurs Hormonal Interactions During a 28-Day Ovarian Cycle Day 1: GnRH release of FSH and LH FSH and LH growth of several follicles, and estrogen release estrogen levels Inhibit the release of FSH and LH Stimulate synthesis and storage of FSH and LH Enhance further estrogen output Hormonal Interactions During a 28-Day Ovarian Cycle Estrogen output by the vesicular follicle increases High estrogen levels have a positive feedback effect on the pituitary at midcycle Sudden LH surge at day 14 Hormonal Interactions During a 28-Day Ovarian Cycle Effects of LH surge Completion of meiosis I (secondary oocyte continues on to metaphase II) Triggers ovulation Transforms ruptured follicle into corpus luteum Hormonal Interactions During a 28-Day Ovarian Cycle Functions of corpus luteum Produces inhibin, progesterone, and estrogen These hormones inhibit FSH and LH release Declining LH and FSH ends luteal activity and inhibits follicle development Hormonal Interactions During a 28-Day Ovarian Cycle Days 26–28: corpus luteum degenerates and ovarian hormone levels drop sharply Ends the blockade of FSH and LH The cycle starts anew Figure Hypothalamus Late follicular and luteal phases 1 1 2 2 2 3 4 5 5 6 8 8 7 Slightly elevated estrogen and rising inhibin levels. Positive feedback exerted by large in estrogen output. Mature follicle Corpus luteum Ovulated secondary oocyte Ruptured follicle LH surge Progesterone Estrogen Inhibin Hypothalamus Early and midfollicular phases Travels via portal blood Granulosa cells Inhibin Androgens Convert androgens to estrogens Thecal cells Anterior pituitary GnRH FSH

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